Roof Rack / Cargo Carrier over sunroof?

I'm in the process of planning a cross country road trip, and we'll be taking my Elantra. We're going to be a bit tight on space (2 adults, 1 kid, and 3 kitties) so we're looking for ways to expand a bit to carry the necessities.

I've looked into adding a hitch and trailer but this makes me feel very uncomfortable especially given the chance it might void warranty repairs. So instead I was thinking a roof rack or cargo carrier.

Is there any issue putting one over the sunroof? Is there a preferred brand that might work better for this?

Thanks for any advice or experiences with this.